PRINCETON   UNIVERSITY   CONTRIBUTION   TO   THE 
GEOLOGY  OF  NEWFOUNDLAND— NO.  5 


Pre-Cambrian  Rocks  of  South 
east  Newfoundland 


BY 

ARTHUR  FRANCIS  BUDDINGTON 


A  DISSERTATION 

PRESENTED  TO  THE  FACULTY  OF  PRINCETON  UNIVERSITY 

IN  CANDIDACY  FOR  THE  DEGREE  OF  DOCTOR 

OF  PHILOSOPHY,  APRIL,  1916 


Reprinted  from  the  JOURNAL  OF  GEOLOGY,  Vol.  XXVII,  No.  6 
September-October,  1919,  pp.  449-79 


Pre-Cambrian  Rocks  of  South 
east  Newfoundland 


A  DISSERTATION 

PRESENTED  TO  THE  FACULTY  OF  PRINCETON  UNIVERSITY 

IN  CANDIDACY  FOR  THE  DEGREE  OF  DOCTOR 

OF  PHILOSOPHY,  APRIL,  1916 


BY 
ARTHUR  FRANCIS  BUDDINGTON 


EARTH 

SCIENCE* 

LIBRARY 


Accepted  by  the  Department  of  Geology, 
April,  1916 


PRE-CAMBRIAN  ROCKS  OF  SOUTHEAST 
NEWFOUNDLAND1 


A.  F.  BUDDINGTON 
Brown  University 


The  following  paper  gives  the  more  important  results  of  an 
investigation  based  upon  field  work  carried  on  during  the  summers 
of  1913  and  1914. 

Southeastern  Newfoundland  is  important  geologically  in  that  it 
affords,  as  far  as  is  known,  the  most  complete  section  of  the  later 
pre-Cambrian  rocks  along  the  eastern  coast  of  North  America, 
and  an  understanding  of  this  section  should  aid  in  the  correlation 
of  the  later  pre-Cambrian  at  other  localities.  The  term  later 
pre-Cambrian,  as  here  used,  is  possibly  the  equivalent  of  the  terms 
Proterozoic  or  Algonkian. 

LOCATION  AND   GEOGRAPHY 

The  Avalon  Peninsula  (Fig.  i)  forms  the  southeastern  portion 
of  Newfoundland  and  is  attached  to  the  main  island  by  a  narrow, 
rugged  isthmus,  in  places  but  three  miles  wide,  which  separates 
Trinity  Bay  on  the  north  from  Placentia  Bay  on  the  south.  The 
peninsula  itself  is  in  turn  almost  split  in  twain  again  by  St.  Mary's 
and  Conception  bays.  The  major  portion  of  the  rocks  here 
described  lie  along  the  eastern  side  of  Conception  Bay,  at  the  head 
of  this  bay,  and  in  the  vicinity  of  St.  John's;  but  they  are  believed 
to  be  typical  of  the  entire  peninsula  and  of  the  later  pre-Cambrian 
rocks  of  eastern  Newfoundland  in  general. 

Except  for  the  mining  industry  conducted  on  a  large  scale  at 
Great  Bell  Island  in  Conception  Bay,  fishing  is  almost  the  sole 
occupation  of  the  inhabitants.  As  a  consequence  of  this  and  of  the 
unfavorable  character  of  the  interior  of  the  peninsulas,  habitations 

1  Thesis  presented  to  the  faculty  of  Princeton  University  for  the  degree  of  Doctor 
of  Philosophy. 

449 


444308 


45° 


A.  F.  BUDDINGTON 


are  confined  almost  exclusively  to  the  shore  lines,  and  often  to  small 
valleys  at  the  mouths  of  brooks  which  may  be  from  a  fraction  of  a 
mile  to  several  miles  apart. 


Geological  and  Submarine 
ToDoaraphical    Map  of 

Newfoundland^^  ^ 


FIG.  i 


LITERATURE 


The  literature  on  Newfoundland  pre- Cambrian  geology  is  well 
summarized  by  Van  Hise  and  Leith  ( 1 909) .  Jukes  ( 1 843 ,  p.  5 1 )  first 
separated  the  Cambrian  from  the  pre-Cambr-ian  and  noted  the 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  451 

unconformity  existing  between  them.  He  was  followed  by  Murray 
(1881),  who  gives  accurate  descriptions  of  the  pre-Cambrian  sedi- 
ments and  classes  them  as  the  intermediate  series,  possibly  equiva- 
lent to  the  Huronian  of  Canada.  Walcott  (1899,  p.  219)  proposed 
the  name  Avalon  for  the  terrane  lying  between  the  basal  beds  of 
the  Cambrian  and  the  Archean  gneisses  of  Newfoundland .  Walcott 
(1900)  described  a  new  pre-Cambrian  terrane  conformable  above 
the  Signal  Hill  series,  which  he  called  the  Random  and  included  in 
the  Avalon  terrane.  Howley  (1907)  published  a  map  in  which  he 
outlined  the  distribution  of  the  Avalonian  series  and  also  distin- 
guished a  formation  composed  of  interbedded  volcanics  and  aqueous 
deposits,  which  he  separated  from  the  base  of  the  Avalonian  terrane 
and  called  Lower  Huronian.  The  succession  worked  out  by  Murray 
and  Howley,  the  addition  by  Walcott,  and  the  modification  pro- 
posed by  Howley  are  given  below. 

Feet 

Random                  Sandstones,  quartzitic  sandstones,  and  sandy  shales  i  ,000 

Red  conglomerate  500 

Signal  Hill              Dark-red  sandstones  1,320 

Greenish  or  gray  fine-grained  sandstones  1,300 

Momable  slates     Dark-brown  or  blackish  slates  2,000 

Torbay  slates         Green,  purple,  pinkish,  or  red  slates  3,300 

Conception  slates  Greenish  slates 

Lower  Huronian    Mixed  igneous  and  aqueous  deposits  in-a  highly  meta- 
morphosed condition 

PHYSIOGRAPHY 

In  general,  the  striking  features  of  the  Avalon  Peninsula  are  the 
parallel  lineaments  of  the  topography;  the  ever-present,  bold, 
rocky  cliffs  of  the  coast ;  the  flat-topped  uplands  with  innumerable 
lakes  and  ponds  (Jukes  counted  153  from  the  top  of  Powder  Horn 
Mountain);  and  the  fiord  bays  with  their  deep  interiors  and 
shallower  thresholds. 

The  topography  is  that  of  a  much-dissected  plateau  at  an 
altitude  of  from  500  to  700  feet,  with  monadnocks  rising  to  heights 
of  1,000  to  1,100  feet,  and  submerged  river  valleys  deeply  gouged  by 
glaciers  and  invaded  by  the  sea,  constituting  fiord  bays  and  their 
arms.  The  remnants  of  two  definable  peneplains  may  be  repre- 
sented in  the  present  topography:  one  on  the  highland  peneplain 


452  A.  F.  BUDDINGTON 

of  the  plateau  surface  (Fig   2),  the  other  represented  in  the  broad 
river  valleys  and  lowlands  at  a  height  of  250  to  300  feet. 

The  trend  lines  of  the  more  impressive  and  marked  physio- 
graphic features  have  been  controlled  for  the  greater  part  by  the 
presence  of  ancient  fault  and  fracture  lines,  which  have  to  a  large 
extent  determined  the  distribution  of  the  underlying  rocks,  with 
their  varying  degrees  of  resistance  to  erosion  and  weathering  and 
the  consequent  parallel  lineaments  of  the  present  topography. 
Joints  have  certainly  played  a  prominent  part  in  localizing  the 
erosive  agents. 


FIG.  2. — Highland  peneplain  on  granite;    interior  of  the  St.  John's  Peninsula; 
about  eight  miles  east  of  Holyrood. 


An  uplift  of  the  land  following  the  period  of  glaciation  is  indi- 
cated by  several  facts.  The  amount  of  this  uplift  has  been  stated 
by  Daly  (1891,  pp.  257-58),  judging  from  the  lower  limit  of  undis- 
turbed glacial  erratics  at  St.  John's,  to  be  about  575  feet;  but  the 
presence  of  perched  bowlders  in  precarious  positions  on  the  tops  of 
hills  at  much  lesser  elevations  (especially  at  about  300  feet) 
around  Conception  Bay  renders  this  estimate  of  doubtful  value. 

GLACIATION 

The  results  of  glaciation  expressed  in  the  present  topography 
point  to  the  presence  of  local  ice  caps  flowing  into  the  individual 
bays  in  a  direction  perpendicular  to  the  major  outlines  of  the  bays 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  453 

at  each  point,  and  hence  controlled  in  a  great  degree  by  the  gross 
features  of  the  pre-glacial  topography.  The  directions  of  ice 
movement  are  easily  decipherable  from  the  abundant  striations, 
the  stoss  and  lee  sides  of  hills  (Fig.  3),  and  numerous  bowlder 
trains  which  may  be  traced  to  their  source. 

Every  bay  indenting  the  coast  of  the  Avalon  Peninsula  presents 
all  the  essential  characteristics  of  a  fiord,  such  as  high,  steep, 
straight,  parallel  walls,  threshold  across  its  mouth,  and  small, 
insignificant  streams  entering  its  head.  In  Trinity  Bay  (Fig.  i) 
the  inner,  deepest  portion  is  over  1,100  feet  deeper  than  the  sill 
across  the  mouth.  Where  the  relations  are  known  there  is  a  remark- 
able parallelism  between  the  strike  of  the  major  fault  planes  and 


FIG.  3. — Glaciated  hills  with  lee  and  stoss  sides  southeast  of  Harbour  Main, 
Conception  Bay.    Lee  sides  are  on  the  north-northeast  ends  of  hills. 

the  trend  of  the  coast  line,  but  the  writer  could  find  no  evidence 
that  faulting  was  directly  responsible  for  the  formation  of  the 
fiords.  The  faults  and  fractures  controlling  the  lineaments  of  the 
bays  are  of  ancient  date— older  than  the  peneplains — and  their 
influence  on  the  present  topography  has  been  indirect.  The 
formation  of  the  sills  across  the  mouths  of  the  bays  by  deposits  from 
currents  is  improbable,  since  this  theory  will  not  hold  for  the  inland 
fiords  of  Gander  Lake,  Red  Indian  Lake,  or  Grand  Lake,  the  latter 
with  its  deepest  part  not  less  than  988  feet  below  sea-level  and  with 
its  outlet  116  feet  above  sea-level.  In  view  of  these  conditions 
glacial  overdeepening  of  river  valleys  probably  associated  with  some 
submergence  followed  by  the  invasion  of  the  sea  seems  the  best- 
adapted  explanation  for  these  fiord  bays 


454  A.  F.  BUDDINGTON 

GENERAL   GEOLOGY 

The  later  pre-Cambrian  beds  have  undergone  at  least  two 
periods  of  folding,  one  at  the  close  of  the  later  pre-Cambrian, 
possibly  the  Penokean  revolution,  as  denned  by  Blackwelder 
(1914),  the  other  the  Taconic.  As  a  consequence  of  this,  and  of 
probable  later  movements,  the  beds  are  much  disturbed,  more  or 
less  closely  folded,  and  very  considerably  faulted.  The  core  of  a 
major  anticline  composed  of  complexly  faulted  and  folded  beds  of 
the  volcanic  series,  cut  across  at  a  small  angle  by  a  stock  of  grano- 
diorite,  is  exposed  at  the  head  of  Conception  Bay.  At  Chapel  Cove 
its  eroded  surface  is  overlain  by  beds  constituting  the  south  end  of  a 
northward-pitching  synclinal  fault  block  of  Cambrian  sediments,  in 
which  Conception  Bay  is  excavated.  We  have  here  apparently  the 
phenomenon  of  the  location  of  a  younger  syncline  in  sediments 
deposited  in  a  basin  on  the  eroded  crest  of  an  anticline. 

Cutting  across  the  east  flank  of  the  anticline  is  a  batholith  of 
granite  forming  the  backbone  of  the  St.  John's  Peninsula  and  called 
by  the  writer  the  Holyrood  granite  batholith.  This  is  bordered  on 
the.  east  by  a  narrow  band  of  the  volcanics  overlain  by  successively 
higher  beds  involved  in  minor  folds  until  the  trough  of  a  major 
syncline  in  the  Signal  Hill  series  is  reached  east  of  St.  John's. 
According  to  Murray  and  Howley's  map  of  1881  the  Carbonear 
Peninsula  is  formed  of  later  pre-Cambrian  beds  which  overlie  the 
volcanics  and  are  involved  in  two  major  synclines  in  the  troughs  of 
which  the  Signal  Hill  series  appears,  with  an  intervening  anticline 
on  the  core  of  which  the  Torbay  series  appears.  The  Placentia 
Peninsula,  according  to  the  same  map,  is  composed  of  a  syncline  of 
beds  in  the  trough  of  which  the  Signal  Hill  series  lies,  while  the 
volcanic  series  forms  its  western  border  and  appears  on  the  flank 
of  an  anticline. 

Metamorphism,  although  not  extreme,  has  yet  affected  the  rocks 
to  a  considerable  degree.  The  beds  lie  in  folds  which,  although, 
probably  not  closed,  yet  approach  that  state,  and  a  slaty  cleavage 
at  an  angle  to  the  bedding  is  prevalent  throughout  the  entire  bedded 
series.  Along  localized  zones  basaltic  flows  and  breccias  have  been 
changed  to  chloritic  schists,  and  rhyolite  flows  have  been 
analogously  altered  to  pinite,  quartz-pyrophyllite,  or  pyrophyllite 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  455 

schists  (Buddington,  1916).  Yet  the  granite,  granodiorite,  and 
many  of  the  volcanics  show  little  or  no  affects  of  metamorphism  and 
are  quite  unaltered. 

Whereas  metamorphism  has  been  a  moderate  factor,  however, 
faulting  on  a  tremendous  scale  and  often  of  remarkable  intensity 
has  been  the  predominating  feature  of  the  diastrophic  processes. 
These  faults  trend  in  the  main  a  little  east  of  north,  and  the  throw 
along  many  of  them  is  measurable  in  thousands  of  feet.  A  few  of 
the  more  important  ones  are  the  fault  between  the  Cambrian  and 
pre-Cambrian  along  the  east  side  of  Conception  Bay  from  Topsail 
to  Cape  St.  Francis,  with  a  throw  of  8,000  feet,  as  determined  by 
van  Ingen;  the  fault  a  short  distance  inland  from  the  west  side  of 
Colliers  Bay  in  Conception  Bay,  which  may  be  traced  for  almost  ten 
miles  and  separates  the  Cambrian  from  the  pre-Cambrian  and  the 
Conception  slates  from  the  volcanic  series;  and  lastly,  the  fault  on 
the  west  side  of  Random  Sound,  which  may  be  traced  for  fifteen 
miles  and  brings  Cambrian  beds  against  pre-Cambrian  granite  and 
the  Conception  slate  series. 

UNCONFORMITY   BETWEEN   CAMBRIAN   AND    LATER   PRE-CAMBRIAN 

The  uncomformable  relations  of  the  Lower  Cambrian  beds  to 
those  of  the  later  pre-Cambrian,  with  the  possible  exception  of  the 
Random  formation,  can  be  definitely  established.  At  eleven  widely 
separated  localities  in  Conception  Bay  the  actual  unconformable 
plane  of  contact  between  the  Lower  Cambrian  and  the  later  pre- 
Cambrian  may  be  observed. 

At  Brigus  the  Lower  Cambrian  rests  with  an  angular  uncon- 
formity on  the  upturned  beveled  edges  of  members  of  the  Avondale 
volcanic  series.  Along  Colliers  Bay  the  Lower  Cambrian  with  a 
gentle  dip  rests  unconformably  on  more  or  less  vertical  basalt  flows 
and  breccias  of  the  Avondale  volcanic  series.  At  Chapel  Cove  the 
Lower  Cambrian  beds  rest  on  the  eroded  surface  of  a  quartz  syenite 
and  contain  pebbles  of  the  underlying  rock.  At  Duff's  Station  the 
Lower  Cambrian  overlies  granite,  occupying  hollows  and  filling 
deep,  narrow  wedgelike  spaces  between  joint  planes  so  as  to  resemble 
a  network  of  veins  on  the  surface.  At  Upper  Gullies  it  rests  with 
unconformable  relations  on  a  gabbro  mass.  On  Kelligrews  Brook 


456  A.  F.  BUDDINGTON 

a  chloritized  granite  gneiss  is  overlain  by  Cryptozoan  limestone 
beds  of  Lower  Cambrian  age.  Just  west  of  Manuels  three  exposures 
of  the  unconformable  relations  are  presented.  At  the  first  locality 
limestone  rests  unconformably  on  granite  and  on  a  rhyolite  dike 
in  the  granite.  A  shale  bed  of  Cambrian  age  overlaps  the  limestone 
and  also  rests  directly  on  the  granite  and  contains  pebbles  of  it. 
A  near-by  conglomeratic  limestone  consists  almost  entirely  of 
cobbles  of  rhyolite  similar  to  the  rock  of  the  rhyolite  dike.  At  the 
second  locality  a  deep-fissure  deposit  of  conglomeratic  limestone 
with  pebbles  of  the  country  rock  occurs  in  diabase.  At  the  third 
locality  a  Lower  Cambrian  conglomeratic  limestone  carrying 
Hyolithes  and  Coleoloides  rests  on  dark-red  rhyolite,  the  pebbles 
consisting  almost  entirely  of  the  underlying  rock.  Again,  in  the 
bed  of  Manuels  Brook  a  coarse  conglomerate  rests  unconformably 
on  volcanics  and  on  a  granite  dike  intrusive  in  the  volcanics.  The 
conglomerate  is  of  Lower  Cambrian  age  and  consists  of  cobbles  and 
bowlders  of  the  underlying  granite  and  volcanics. 

On  Trinity  Bay,  along  Smith  and  Random  sounds,  the  Lower 
Cambrian,  of  older  age  than  that  on  Conception  Bay,  rests  discon- 
formably  on  beds  of  the  Random  formation  in  the  trough  of  a 
syncline.  The  Random  may  be  either  conformable  or  disconform- 
able  with  the  Signal  Hill  series.  In  either  case  the  Lower  Cambrian 
must  be  unconformable  with  the  Signal  Hill  series  and  all  lower 
formations,  since  it  must  necessarily  have  transgressed  all  the  later 
pre-Cambrian  formations  in  passing  from  its  disconformable  posi- 
tion on  the  Random,  the  youngest  formation  of  the  pre-Cambrian, 
in  the  trough  of  a  syncline,  across  the  flank  of  an  anticline  on  to  the 
lowest  later  pre-Cambrian  formation,  the  Avondale  volcanics,  on 
the  core  of  an  anticline  in  Conception  Bay. 

AVONDALE   VOLCANICS 

Howley  (1907)  mapped  a  series  of  rocks  which  he  called 
Huronian  and  described  "as  composed  of  mixed  igneous  and 
aqueous  deposits  in  a  highly  metamorphosed  condition."  Parallel 
to  their  trend  they  are  mapped  by  Howley  as  outcropping  for  a 
distance  of  about  two  hundred  miles  in  a  north-northeast-south- 
southwest  direction,  being  submerged  beneath  the  sea  at  each  end. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  457 

In  view  of  the  unknown  age  of  this  formation,  and  because  of  its 
characteristic  development  and  typical  outcrops  in  the  vicinity  of 
Avondale,  Conception  Bay,  the  writer  proposes  the  name  Avondale 
volcanics  to  designate  this  series,  which  comprises  rocks  of  direct 
volcanic  origin,  together  with  a  small  amount  of  interbedded  more 
or  less  water  worn  volcanic  materials.  They  constitute  a  formation 
of  wide  geographical  extent — 200  miles  along  the  strike  and  100 
miles  or  more  across  the  strike — and  of  great  but  unknown  thick- 
ness, at  least  several  thousand  feet,  forming  so  far  as  is  known  the 
basal  member  of  the  later  pre-Cambrian  or  Avalonian  system  of 
Newfoundland.  Interbedded  rhyolite  and  plagioclase  basalt  flows, 
with  corresponding  breccias,  crystal,  lithic,  and  vitric  tuffs,  volcanic 
dust  beds,  and  average  tuffs,  together  with  volcanic  conglomerates, 
sandstones,  and  slates  are  comprised  within  the  series. 

The  beds  are  in  a  highly  disturbed  condition,  with  a  prevailing 
steep  dip,  and  are  affected  by  intense  and  often  profound  faulting. 
They  are  exposed  on  the  cores  of  major  anticlines  or  are  brought  to 
the  surface  on  the  upthrow  sides  of  great  faults.  The  degree  of 
metamorphism  which  the  rocks  have  suffered  is  in  general  moderate, 
though  locally  intense,  and  is  manifest  for  the  larger  part  merely 
in  the  development  of  a  slaty  cleavage.  Secondary  minerals,  except 
those  of  surface  origin,  are  confined  almost  exclusively  to  sericite 
and  quartz  in  the  acid  rocks  and  chloride  with  sericite,  epidote,  and 
calcite  in  the  basic  rocks.  Along  certain  shear  zones  in  the  acid 
rocks  pyrophyllite,  quartz-pyrbphyllite,  and  pinite  schists  have 
formed  through  replacement,  while  in  certain  basic  rocks  copper 
ores  have  been  deposited  along  close-set  narrow  fractures  and  in 
vesicles  of  the  flows.  Ore  in  quantities  of  commercial  importance, 
however,  has  not  yet  been  found. 

In  view  of  the  great  age  of  the  rocks  the  lack  of  intense  meta- 
morphism and  the  frequent  preservation  of  delicate  primary 
structures  are  striking.  Indeed  there  is  little  doubt  that,  with 
search,  practically  every  structure  and  texture  found  in  the  Tertiary 
and  recent  volcanics  might  also  be  found  in  these  ancient  pre- 
Cambrian  volcanics. 

One  of  the  most  interesting  discoveries  in  this  series  was  the 
presence  of  volcanic  necks  intruded  through  the  breccias  and  tuffs. 


458  A.  F.  BUDDINGTON 

Near  Manuels  a  plug  of  plagioclase  basalt  about  400  by  450  feet, 
with  columnar  jointing  perpendicular  to  the  surface  and  with  dikes 
and  apophyses  radiating  from  it  into  the  adjoining  rocks,  was  found 
intruded  through  basaltic  and  rhyolitic  breccias.  A  rhyolite  neck 
about  fifty  feet  in  diameter  and  circular  in  shape,  nearly  every  foot 
of  the  contact  of  which  could  be  seen,  and  a  neck  of  basic  tuff  with 
fragments  up  to  three  feet  in  diameter  of  the  underlying  rocks, 
through  which  it  was  drilled,  and  with  radiating  dikes  of  tuff,  were 
also  found.  The  largest  neck  forms  a  conspicuous  hill  about  three 
miles  south  of  Holyrood  and  seems  to  have  been  one  of  the  main 
centers  of  volcanic  activity  in  this  region.  Here  we  find  a  great 
elliptical  stock  of  rhyolite  porphyry  about  a  mile  long  and  half  a 
mile  wide,  while  in  the  surrounding  country  occur  exceptionally 
coarse  rhyolite  breccias,  with  many  blocks  up  to  two  feet  in  diam- 
eter, interbedded  with  rhyolite  flows  and  tuffs.  A  chemical  analysis 
of  this  rock,  given  below,  shows  it  to  be  very  similar  to  the  rhyolite 
flows  at  Manuels. 

TABLE  I 

CHEMICAL  ANALYSIS  or  RHYOLITE  PORPHYRY  FROM  VOLCANIC 
NECK  SOUTH  OF  HOLYROOD 

SiO2 75.85      K2O 4.47 

A1A 13 .03      H2O+ 35 

Fe2O3 i  .82      H2O- 05 

FeO *..      .32      MnO 05 

MgO 05 

GaO 38  Total 99.71 

NaaO... :.../ 3-34 

The  rhyolite  flows  are  quite  variable  in  color,  ranging  through 
reddish,  purplish,  and  greenish  grays.  They  are  usually  aphanitic 
in  texture,  and  dense,  chertlike  in  character,  sometimes  felsitic,  with 
a  finely  rough  feel.  They  may  be  homogeneous  and  massive,  or 
may  be  marked  by  beautiful,  well-developed,  and  well-preserved 
banded  textures,  and  are  very  frequently  spherulitic.  The  spheru- 
lites  vary  from  microspherulites  up  to  those  as  large  as  a  man's  head, 
or  even  occasionally  attain  a  diameter  of  two  feet  (Fig.  4),  but  in 
general  they  are  of  medium  size  (Fig.  5).  The  flows  may  also  be 
characterized  by  a  platy  jointing  more  or  less  parallel  to  the  flowage 
planes,  or  by  flow  breccia,  eutaxitic  (Fig.  6),  or  perlitic  structures. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND 


459 


As  seen  in  thin  section  the  texture  is  usually  microgranitic  or  an 
irregular  polarizing  aggregate  of  quartz  and  feldspar.  Spherulitic, 
axiolitic,  and  microspherulitic  textures  are  common,  and  rarely  a 
felt  of  microlitic  feldspars  in  a  groundmass  of  quartz  is  observed. 
A  micrographic  texture  characterizes  portions  of  an  eutaxite  from 


FIG.  4. — Very  coarsely  spherulitic  rhyolite;   the  largest  spherulite  is  twenty-two 
inches  in  diameter;  about  five  and  one- half  miles  south  of  Manuels,  Conception  Bay. 

near  Avondale.  A  chemical  analysis  of  a  specimen  from  a  50-foot 
rhyolite  flow  follows.  The  rock  is  a  dense,  red,  banded  felsite  with 
a  microfelsitic  to  finely  macrocrystalline  and  micropoikilitic  texture. 

TABLE  II 
CHEMICAL  ANALYSIS  or  RHYOLITE  FROM  FLOW  AT  MANUELS 


SiO2 76 . 24 

A12O3 .13.94 

Fe2O3 89 

FeO.. 13 

MgO 27 

CaO 1.07 


Na20 2.55 

K2O 4-95 

H20+ 15 

H20- 03 


Total..  ..100.22 


460 


A.  F.  BUDDINGTON 


FIG.  5.— Medium  spherulitic  banded  rhyolite;    about  five  and  one-half  miles 
south  of  Manuels,  Conception  Bay.     Photograph  by  G.  v.  I. 


I 


•'W^fv     -JH*  x-  «*   * 

i  Oi 

v'-:l:;i^.:::;: 


•   •'    f  V» 


FIG.  6. — Microphotograph  of  eutaxitic  structure  in  rhyolite.    Hill  467,  south 
of  Avondale,  Conception  Bay.    Natural  light,  X$2  diameters. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND 


461 


Basalts  attain  a  tremendous  development  along  Colliers  Bay, 
extending  south  toward  Brigus  Junction.  They  are  associated 
with  a  great  development  of  basaltic  breccias  and  often  exhibit 
amygdaloidal  or  Howage  structures.  The  flows  are  very  much 
altered  throughout  and  may  be  chloritized  with  resultant  green- 
gray  rocks,  or  hydrated  and  thoroughly  impregnated  with  iron  oxide 
giving  purplish-  or  reddish-brown  hues.  These  alterations  are 
probably  due  to  thermal  waters,  as  they  occur  independent  of  what 


FIG.  7. — Coarse  rhyolite  breccia;  about  two  and  one-half  miles  south  of  Man- 
uels,  Conception  Bay.  Photograph  by  G.  v.  I. 

might  be  expected  as  the  result  of  weathering.  In  texture  they 
vary  from  felsitic  to  finely  porphyritic,  and  in  thin  section  show  a 
felt  of  plagioclase  laths  or  microlites  with  a  distinct  fluxion  structure 
in  a  chloritic  or  indistinct  altered  groundmass.  Chlorite  pseudo- 
morphs,  replacements  of  some  ferromagnesian  mineral,  possibly 
augite,  occur  as  abundant  minute  phenocrysts  in  some  flows. 

The  breccia  beds  exhibit  a  varied  assortment  of  colors  and  a  wide 
range  in  the  diameter  of  their  component  fragments;  but  by  far  the 
predominant  portion  of  the  rhyolitic  breccias  are  various  hues  and 
tones  of  reddish-  and  purplish-gray,  whereas  the  basaltic  breccias 


462 


A.  F.  BUDDINGTON 


consist  of  dark  greenish-gray  fragments  in  dark  reddish-,  purplish-, 
or  greenish-gray  matrices. 

Both  basaltic  and  rhyolitic  breccias  exhibit  approximately  the 
same  range  in  the  diameter  of  their  fragments,  from  a  fraction  of  an 
inch  to  four  feet  (Figs.  7  and  8).  The  general  run  of  the  fragments 


FIG.  8. — Coarse  basalt  breccia;  west  side  of  Blue  Hills,  south  of  Conception  Bay 

would  probably  average  a  few  inches  in  diameter.  In  general,  the 
rhyolitic  breccias  and  the  basaltic  breccias  contain  few  foreign 
fragments,  especially  the  coarser  beds;  yet  beds  in  which  angular 
fragments  of  rhyolite  and  basalt  and  crystals  of  orthoclase  and 
plagioclase  are  mingled  are  frequent;  and  rhyolitic  breccias  and 
basaltic  breccias  are  often  found  interbedded. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND 


463 


Crystal  tuffs  are  of  frequent  occurrence  interbedded  with  the 
breccias  and  tuffs.  They  are  remarkable,  in  view  of  their  great  age 
and  the  vicissitudes  which  they  have  undergone,  for  the  frequent 
presence  of  a  perfectly  preserved  vitroclastic  structure  in  their 
groundmass,  whether  rhyolitic  or  basaltic  in  nature.  These 
devitrified  glass  shards  are  such  a  prominent  feature  of  some  of  the 
tuffs  from  the  vicinity  of  Red  Rock  Lake  near  Brigus  that  they 


JTIG  g — Microphotograph  of  vitroclastic  groundmass  of  rhyolitic  crystal  tuff; 
near  Red  Rock  Lake,  south  of  Brigus,  Conception  Bay.  Natural  light,  Xs6  diam- 
eters. 

might  well  be  denominated  vitric  tuffs  (Fig.  9).  In  other  cases  the 
groundmass  is  an  indistinct,  microcrystalline,  granular  dust. 
Many  of  these  tuffs  are  soaked  with  hematite  and  hence  are  reddish 
in  color.  Associated  with  the  phenocryst-like  crystals  are  frag- 
ments of  either  porphyritic  or  felsitic  basalt  or  rhyolite,  or  of 
devitrified  obsidian  exhibiting  trichites,  microspherulites,  spheru- 
lites,  axiolites,  perlitic  cracks,  pumiceous  structure,  or  any  combina- 
tion of  these.  The  crystals  consist  principally  of  plagioclase  and 


464 


A.  F.  BUDDINGTON 


orthoclase,  with  quartz  and  magnetite  in  the  acid  tuffs,  and  of 
plagioclase,  augite,  magnetite,  apatite,  and  foreign  crystals  in  the 
basic  tuffs.  Some  of  the  basic  tuffs  resemble  typical  palagonite 
tuffs  (Fig.  10). 

The  lithic  tuffs  consist  predominantly  of  fragments  of  rhyolite 
or  of  pilotaxitic  basalt,  according  to  their  nature,  in  a  groundmass 


FIG.  10. — Groundmass  of  basaltic  crystal  tuff,  with  devitrified  shards  of  glass 
bordered  by  rims  of  fibrous,  brownish  material.  Hill  937  near  Holyrood.  Micro- 
photograph.  Natural  light. 

consisting  of  finely  comminuted  materials  similar  to  the  lithic 
fragments,  with  crystals  of  feldspar  and  quartz  in  minor  amount. 
The  volcanic-dust  beds  are  frequently  well  bedded  and  chertlike 
in  character,  often  translucent  in  thin  edges,  with  a  conchoidal  to 
subconchoidal  fracture. 

The  waterworn  volcanics  comprise  volcanic  conglomerates, 
sandstone,  and  a  rare  red  shale  bed.  The  prevalence  of  volcanic 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  465 

conglomerates,  both  stratigraphically  and  geographically,  inter- 
bedded  with  the  volcanic  breccias,  flows,  and  tuffs,  is  one  of  the  most 
cogent  arguments  for  the  subaerial  origin  of  the  volcanic  series  as  a 
whole;  for  both  basalt  and  rhyolite  conglomerates  are  associated 
with  and  interbedded  between  completely  angular  basalt  breccias 
and  well-rounded  basalt  conglomerates,  and  between  similar  angular 
rhyolite  breccias  and  well-rounded  rhyolite  conglomerates.  In 
some  of  the  basalt  conglomerate  beds  bowlders  up  to  three  feet  or 


FIG.  ii. — Basalt  volcanic  conglomerate;  Turks  Gut,  Colliers  Bay,  Conception 
Bay.  Photograph  by  G.  v.  I. 

more  in  diameter  are  not  rare  (Fig.  n).  Such  beds  are  in  places 
200  feet  thick  and  grade  upward  or  downward  into  sandstones  or 
tuffs.  Some  of  the  sandstone  beds  are  cross-bedded  and  contain 
abundant  fragments  of  red  shale  constituting  typical  thon-gallen 
beds.  Others  are  ripple  marked,  but  these  features  are  rare. 

In  the  course  of  the  work  no  reasons  were  found  for  assuming  the 
volcanics  to  have  had  other  than  an  essentially  subaerial  origin.  All 
the  structures  and  textures  of  the  flows  and  the  characters  of  the 
associated  volcanic  products  are  compatible  with  such  a  hypothesis, 
while  the  particular  criteria  pointing  to  such  a  conclusion  are  as 
follows : 


466  A.  F.  BUDDINGTON 

The  predominance  and  widespread  distribution  of  the  red  and 
brown  volcanic  tuffs  and  breccias,  which  owe  their  color  to  satura- 
tion and  cementation  with  hematite,  point  toward  subaerial 
exposure  rather  than  toward  local  effects  of  volcanic  gases. 

The  constant  association  of  volcanic  conglomerates  or  sandstone 
with  the  breccias,  tuffs,  and  flows  indicates  the  work  either  of  river 
erosion,  or  wave  work,  or  both.  The  first  seems  'more  probable  in 
view  of  the  constant  recurrence  of  conglomerate  beds  in  the  strati- 
graphic  succession,  as  well  as  the  fact  that  beds  of  conglomerate 
150  to  200  feet,  thick  with  well-rounded  bowlders  up  to  three  feet 
in  diameter,  are  exceptional  within  marine  deposits,  even  within 
marine  volcanic  deposits.  On  the  other  hand  such  conglomerates 
are  commonly  found  associated  with  subaerial  volcanics  of  all  ages. 
Those  of  Newfoundland  are  such  as  might  be  expected  to  form  along 
river  valleys  draining  a  region  of  great  active  volcanic  cones  such  as 
this  probably  was.  Although  some  of  the  conglomerates  may  have 
been  deposited  in  standing  water,  the  indications  are  that  for  the 
most  part  they  were  deposited  on  a  land  surface  during  quiescent 
periods  between  successive  volcanic  outbursts  which  repeatedly 
buried  them  with  the  products  resulting  from  extravasation  and 
explosion. 

The  volcanics  are,  so  far  as  known,  the  oldest  formation  of  the 
later  pre-Cambrian  in  this  district.  They  are  intruded  by  granite, 
and  together  with  the  granite  are  overlain  unconformably  by  Lower 
Cambrian  sediments.  The  pre-Cambrian  volcanics  of  the  Blue 
Ridge  of  Virginia  and  Maryland  present  similar  relationships 
(Keith,  1892),  and  in  the  present  state  of  knowledge  it  seems  prob- 
able that  in  early  later  pre-Cambrian  times  a  chain  of  volcanic  cones 
extended  from  Newfoundland  to  North  Carolina  and  farther,  in  a 
zone  more  or  less  parallel  to  the  present  coast  line. 

CONCEPTION    SLATE    SERIES 

The  Conception  slate  series  was  examined  by  the  writer  along 
the  east  side  of  Conception  Bay  from  Portugal  Cove  to  Topsail; 
along  the  west  side,  Colliers  Bay  north  to  Brigus;  near  La  Manche 
on  the  Isthmus  of  Avalon ;  and  along  Smith  and  Random  sounds  on 
Trinity  Bay.  Owing  to  folding,  faulting,  and  covered  exposures 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND 


467 


the  relations  of  this  series  to  the  beds  above  and  below  were  not 
seen. 

The  series  consists  predominantly  of  thin-bedded,  green-gray, 
dense,  halleflinta-like  slates,  at  least  several  thousand  feet  thick, 
which  may  be  compact  without  cleavage,  or  dynamically  meta- 
morphosed, with  a  resultant  well-developed  cleavage;  and  to  a 
lesser  extent  of  green-gray  feldspathic  sandstones  and  conglom- 
erates. The  slates  often  resemble  at  a  superficial  glance  banded 
flow  rhyolites,  but  occasional  sandy  layers  betray  their  true  origin. 

The  slates  may  vary  from  very  fine-grained  or  dense  siliceous 
quartzites  to  argillaceous  slates,  or  from  dense  feldspathic  quartzites 
to  chertlike  feldspathic  slates.  Thin,  intercalated  beds  and  layers 
of  feldspathic  sandstone  are  common,  but  the  predominant  char- 
acter of  the  rocks  is  that  of  a  slate.  The  feldspathic  character  of 
the  typical  slate  and  its  normally  fresh,  undecomposed  character 
are  shown  very  well  by  the  two  chemical  analyses  which  follow.  It 
will  be  noted  that  the  soda  is  in  excess  of  the  potash,  contrary  to 
the  usual  rule  for  sediments  derived  from  well-weathered  materials, 
and  that  the  analyses  resemble  those  of  certain  rhyolites.  The 
high  soda  content  may  be  due  to  plagioclases  washed  in  from  basic 
tuffs. 

TABLE  III 
CHEMIQAL  ANALYSES  or  MEMBERS  or  CONCEPTION  SLATE  SERIES 


i~-_. 

2 

SiO2.  . 

68.92 

77  •  J3 

A12O3  

17.67 

14.01 

Fe2O3 

i  43 

2    25 

FeO 

^  48 

Undet. 

CaO 

8s 

64 

MgO                   

I  .  IO 

36 

Na2O  
K2O    

•     3-oi 
i  .46 

3-59 
i  .01 

Ign.  Loss  

i-75 

.76 

Total         

QO  •  76 

QO  .  7s 

1.  Feldspathic  slate,  near  Brigus,  Conception  Bay. 

2.  Feldspathic  quartzite,  Robinson's  Bight,  Random  Sound,  Trinity  Bay. 

The  sandstones  are  formed  of  angular  to  subangular  grains  of 
quartz,  fresh  plagioclase,  orthoclase,  rhyolite,  plagioclase  basalt, 
and  tuffs.  The  rhyolite  fragments  exhibit  axiolitic,  spherulitic, 
and  banded  textures. 


468  A.  F.  BUDDINGTON 

The  conglomerate  outcrop  near  La  Manche,  and  the  pebbles, 
are  all  of  volcanic  rocks  such  as  basalt,  basalt  porphyry,  rhyolite 
porphyry,  felsite,  etc.,  imbedded  in  a  matrix  showing  innumerable 
flashing  cleavage  faces  of  white  plagioclase. 

Since  these  beds  in  their  well-bedded  and  unoxidized  characters 
give  evidence  of  their  being  deposited  beneath  a  permanent  water- 
level,  and  since  they  consist  almost  exclusively  of  materials  similar 
to  the  rocks  comprised  within  the  underlying  volcanic  series  of 
subaerial  origin,  it  is  probable  that  an  unconformity  exists  between 
the  Conception  slate  series  and  the  Avondale  volcanics,  and  that 
the  former  are  derived  from  the  latter,  at  that  time  a  more  or  less 
loose  accumulation  of  volcanic  ash  and  breccias  which  were  swept 
into  the  sea  in  a  comparatively  fresh  and  undecomposed  condition. 

TORBAY   SERIES 

The  Torbay  series  was  not  studied  by  the  writer.  Murray's 
description  of  it  is  inserted  here  for  completeness: 

Green,  purple,  pinkish,  or  red  slates  in  frequent  alternations;  the  texture 
of  these  slates  is  generally  extremely  fine,  and  in  some  cases  they  approach  in 
hardness  to  jasper  or  chert.  The  fracture  is  often  conchoidal,  and  the  imperfect 
cleavage  parallel  with  the  bedding;  but  in  many  instances  the  rock  has  a  good 
cleavage  at  right  angles  to  the  stratification  and  is  well  adapted  for  roofing 
purposes.  The  exposed  surfaces  weather  for  the  most  part  a  yellowish  white. 

Some  beds  seen  by  the  writer  on  the  Isthmus  of  Avalon  strongly 
resemble  banded  argillites;  cobbles  of  green  and  red  argillite  were 
also  found  in  the  drift  of  the  St.  John's  Peninsula,  presumably 
derived  from-  the  Torbay  series. 

MOMABLE    SERIES 

These  beds  are  described  by  Murray  (1881,  p.  145)  as  follows: 

Dark  brown  or  blackish  slates  of  St.  John's,  with  ripple  marks  very  dis- 
tinctly displayed  on  some  surfaces,  and  in  which  some  obscure  organic  remains 
have  been  found  resembling  those  found  in  c,  and  another  supposed  to  be  the 
shelly  casing  of  some  description  of  Annelid.  The  cleavage  of  this  slate  is 
sometimes  very  regular,  oblique,  or  at  right  angles  to  the  bedding,  but  in  parts 
it  also  cleaves  parallel  with  the  stratification.  Towards  the  top  are  frequent 
layers  of  hard,  fine-grained,  greenish  sandstone  interstratified,  not  usually  over 
6  or  7  inches  in  thickness. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  469 

The  beds  seen  by  the  writer  are  strongly  ripple-marked,  blackish- 
gray,  thin-bedded,  very  fine-grained,  shaly  sandstones,  with  thin 
films  of  black  carbonaceous  or  graphitic  shale.  In  thin  section  the 
sandstone  is  seen  to  be  made  up  of  sharply  angular  grains  of  quartz, 
with  an  occasional  fresh  feldspar  fragment  and  bits  of  carbonaceous 
material.  The  grains  average  about  0.05 'mm.  in  diameter. 

From  a  lithologic  point  of  view  the  most  striking  feature  of  these 
rocks  is  their  content  of  carbonaceous  material,  which,  although 
slight  and  often  absent,  yet  serves  to  contrast  them  with  the  over- 
lying and  underlying  formations.  In  contrast  to  the  succeeding 
reddish-brown  feldspathic  sandstone  formation,  the  gray,  fine- 
grained quartz  sandstones  and  shales  of  the  Momable  suggest  an 
origin  under  a  permanent  water-level  at  shallow  depths  in 
which  flourished  organisms  whose  presence  is  indicated  by  the 
carbonaceous  content  of  the  shales  and  by  the  possible  fossil 
Aspidella. 

Attention  has  been  called  by  many  observers  to  the  resemblance 
between  the  gold-bearing  series  of  Nova  Scotia  and  Murray's 
Intermediate  series  of  Newfoundland.  It  is  to  the  beds  comprising 
the  Conception,  Torbay,  and  Momable  series  lying  below  the  Signal 
Hill  series  and  above  the  Avondale  volcanics  that  this  lithologic 
resemblance  applies.  Judging  from  Fairbault's  descriptions  (Mal- 
com,  1912,  pp.  46-47)  the  Golden ville  quartzites  present  certain 
resemblances  to  the  Conception  slate  series,  the  banded  argillite 
division  of  the  western  part  of  the  field  to  the  Torbay  series,  and 
the  Halifax  formation  to  the  Momable  series.  Specimens  of  the 
Halifax  slate  collected  by  the  writer  from  an  outcrop  in  the  yards 
of  the  Canadian  Pacific  terminal  at  Halifax  are  indeed  indistinguish- 
able, except  for  a  more  prevalent  cleavage,  from  many  characteristic 
specimens  of  the  Momable  series.  Before  any  correlation  may  be 
suggested,  however,  it  is  necessary  that  a  more  intimate  knowledge 
of  the  conformable  or  unconformable  relations  within  the  New- 
foundland series  shall  be  known,  as  well  as  more  definite  information 
concerning  the  relations  of  the  gold-bearing  series  of  Nova  Scotia 
to  the  Cambrian.  The  Momable  beds  are  also  similar  to  the 
Animikie  sediments  as  described  by  Coleman  in  respect  to  their 
content  of  carbonaceous  material. 


470  A.  F.  BUDDINGTON 

SIGNAL  HILL   SERIES 

As  near  as  can  be  judged  from  the  descriptions  of  Murray  and 
Howley  (1881)  and  from  the  experience  of  the  writer  the  Signal  Hill 
series  outcrops  mainly  in  the  troughs  of  synclines  or  synclinoria 
over  an  area  extending  for  a  length  of  about  200  miles  in  a  north- 
northeast-south-southwest  direction  and  about  75  miles  at  right 
angles  to  this. 

The  series  consists  of  a  very  thick  succession  of  reddish-brown, 
occasionally  green,  feldspathic  sandstones  and  conglomerates,  with 
intercalated  shale  beds  and  about  1,300  feet  of  greenish-gray,  thick- 
bedded  feldspathic  sandstones  at  the  base,  giving  a.  thickness 
estimated  at  about  10,000  feet.  Murray's  estimate  of  3,120  feet 
for  this  series  referred  only  to  the  beds  on  the  west  side  of  St.  John's 
harbor,  which  constitute  but  a  part  of  the  series. 

Thon-gallen  or  intraformational  conglomerate  beds  are  abun- 
dant. The  majority  of  the  conglomerate  beds  may  be  appropriately 
described  as  gravel  or  pebble  beds,  with  the  pebbles  varying  in  size 
from  one-fourth  of  an  inch  to  an  inch  in  diameter,  and  prevailingly 
subangular  to  rounded. 

Because  of  the,  predominating  sandy  character  of  such  a 
thick  series  of  sediments;  the  repetition  and  often  considerable 
thicknesses  of  conglomerate  beds;  the  presence  of  so  much  fresh 
plagioclase  and  orthoclase  throughout  the  rocks;  the  prevailing 
subangular  character  of  the  component  grains;  the  predominating 
red  color  due  to  interstitial  hematitic  mud,  to  films  of  hematite, 
and  to  oxidized  grains  of  basalt,  rhyolite,  and  magnetite;  the 
constant  recurrence  of  thon-gallen  beds;  frequent  cross-bedding; 
lithologic  alternations  of  sandstone,  conglomerate,  and  shale;  and 
the  absence  of  any  limestone,  fossils,  or  carbonaceous  materials,  the 
writer  has  been  led  to  conclude  that  these  beds  originated  as  domi- 
nantly  flu  via  tile  deposits  of  subaerial  origin  in  a  subarid  climate. 
It  is  quite  possible  that  the  basal  1,300  feet  of  green-gray  sand- 
stones accumulated  under  a  permanent  water-level;  but  if  so  the 
water  was  apparently  drawn  off  or  excluded  at  the  time  of  accumu- 
lation of  the  succeeding  reddish-brown  series. 

In  thin  sections  from  specimens  of  deep,  livid-brown  sandstone 
from  Signal  Hill  the  rock  is  found  to  consist  of  angular  to  subangular 


PRE-CAM BRIAN  ROCKS  OF  NEWFOUNDLAND  471 

grains  of  quartz,  fresh  plagioclase,  orthoclase,  and  rhyolite  and 
granophyre,  with  rarely  a  fragment  of  basalt.  Accessory  minerals 
comprise  grains  of  primary  epidote  and  occasionally  abundant 
grains  of  magnetite.  A  film  of  hematite  coats  each  grain,  and  in 
some  specimens  the  interstices  are  filled  with  secondary  quartz, 
sericite,  or  occasionally  with  epidote.  The  sericite  is  a  secondary 
product,  the  result  of  recrystallization  during  shearing.  In  one 
section  a  rounded  grain  of  primary  epidote  is  coated  with  a  film 
of  hematite  and  is  surrounded  on  the  outside  of  this  by  a  growth  of 
secondary  epidote.  The  cement  of  the  green  sandstone  seems  to  be 
of  an  epidotic  nature,  apparently  arising  through  a  recrystallization 
of  an  impure  argillaceous  material.  A  chemical  analysis  of  the 
reddish-brown  sandstone  serves  to  confirm  the  highly  feldspathic 
nature  of  this  rock. 

TABLE  IV 

CHEMICAL  ANALYSIS  OF  FELDSPATHIC  BROWN  SANDSTONE  FROM 
NEAR  SIGNAL  HILL,  ST.  JOHN'S 

SiO2 71.38      Na2O 2.28 

A1203 14-25      K20 i .  99 

Fe2O3 4. 75      H2O+ i .  20 

FeO 46      H2O- 21 

MgO 46 

CaO 3.01  Total .  r 99-99 

That  the  red  color  of  the  brown  sandstones  is  due  to  hematite 
and  to  the  oxidation  of  its  iron  content  is  evident  from  a  comparison 
of  the  ferrous  and  ferric  contents  of  the  red  and  green  sandstones. 
Although  both  have  similar  total  contents  of  iron,  4 . 74  and  5.11 
per  cent  respectively,  expressed  in  terms  of  ferrous  iron,  the  brown 
sandstone  shows  4.75  per  cent  of  ferric  oxide  and  only  o  .46  per  cent 
of  ferrous  oxide,  whereas  the  green  sandstone  shows  2 . 54  per  cent 
of  ferric  oxide  and  2  .82  per  cent  of  ferrous  oxide. 

The  red  color  of  the  sandstones  depends  in  varying  degrees  upon 
the  primary  deposition  of  a  hematitic  mud  in  the  interstices  of  the 
sand  grains;  upon  the  deposition  of  hematite  as  a  cement  around 
the  sand  grains;  upon  hematite  existing  in  the  grains  themselves 
as  in  the  cleavage  cracks  of  feldspar,  or  in  oxidized  basalt  and  rhyo- 
lite; and  upon  the  hematite  resulting  from  the  oxidation  of 
magnetite  grains  in  situ. 


472  A.  F.  BUDDINGTON 

The  pebbles  of  the  conglomerates  in  the  vicinity  of  Signal  Hill 
consist  roughly  of  about  three-quarters  rhyolite-porphyry  and  the 
remainder  granophyre,  intraformational  red  shale  flakes,  and  quartz, 
with  occasional  pebbles  of  basalt.  The  rocks  of  which  these  pebbles 
are  formed  are  very  similar  to  the  rocks  comprised  within  the 
Avondale  volcanic  series,  and  it  is  quite  possible  that  they  have  been 
derived  from  that  formation.1 

In  their  stratigraphic  relations,  lithology,  and  mode  of  origin  the 
Signal  Hill  series  resemble  the  Jotnian  of  Sweden,  the  Torridonian 
of  Scotland,  and  the  Keweenawan  of  the  "Canadian  Shield."  In 
the  absence  of  vulcanism,  so  far  as  yet  observed,  they  stand  in 
contrast  to  the  Keweenawan  and  Jotnian,  but  resemble  the  Torri- 
donian. This  is  of  special  interest,  since  it  has  been  shown  by 
Hayes  and  van  Ingen  that  this  district  during  the  succeeding 
Cambro-Ordovician  period  had  a  history  which  coincided  even  in 
minor  detail  with  that  of  Wales. 

INTRUSIVE  ROCKS 

The  later  pre- Cambrian  rocks,  more  especially  the  early  later 
pre-Cambrian  beds,  are  intruded  by  several  batholiths  and  stocks 
of  igneous  rock  and  are  very  intensively  cut  by  dikes.  In  general, 
it  may  be  said  that  the  salic  rocks  have  been  intruded  as  molten 
masses  of  batholithic  or  stock  type,  with  few  apophyses  or  dikes, 
whereas  the  older  basaltic  or  gabbroic  magmas,  to  a  preponderating 
extent,  have  been  intruded  as  dikes. 

The  rocks,  with  the  exception  of  the  quartz  syenite  and  granodi- 
orite,  whose  position  is  unknown,  are  given  in  the  order  of  their 
intrusion,  beginning  with  the  oldest.  Those  around  Conception 
Bay  comprise  hornblende  granite  gneiss,  hornblende  gabbro  and 
plagioclase  gabbro  without  olivine  but  locally  quartz-bearing,  basic 
granodiorite,  biotite  granite  and  granophyre,  quartz  syenite,  aplite 
and  granophyre  dikes  intruding  the  granite,  and  younger  dikes  of 
rhyolite  porphyry  and  diabase  intruding  all  the  older  rocks.  Near 

1  Murray  describes  the  pebbles  of  the  conglomerate  at  Signal  Hill  as  composed 
"chiefly  of  white  quartz,  but  with  occasional  pebbles  of  brown  or  red  jasper,  syenite 
or  gneiss  and  slate."  The  writer  examined  150  pebbles  with  the  entirely  different 
result  given  above. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  473 

Clarenville  on  Trinity  Bay  a  mass  of  gabbro  is  intruded  by  granite, 
and  both  in  turn  are  cut  by  younger  dikes  of  aplite,  rhyolite,  and 
porphyrite  dikes. 

The  hornblende  granite  gneiss  shows  a  cataclastic  texture  and 
is  believed  to  be  the  oldest  rock  in  the  district.  Its  outcrop  was 
noted  in  only  three  areas  of  very  small  extent  along  the  border  of 
the  Holyrood  granite  batholith. 

The  gabbros  occur  as  small,  irregular  patches  on  the  borders  of 
and  within  the  area  of  the  Holyrood  granite  batholith,  and  also  as 
huge  dikes  in  the  Conception  slate  series.  They  are  predominantly 
of  a  blackish  or  dark  speckled  gray  color  weathering  to  an  ashen 
gray.  In  grain  they  vary  from  fine  to  medium,  and  pegmatitic 
facies  are  entirely  lacking.  Mineralogically  there  seem  to  be  two 
types,  which  can  be  distinguished  by  microscopic  methods  alone: 
one  characterized  by  hornblende  without  augite;  the  other  an 
augite  gabbro  in  which  the  pyroxene  may  be  unaltered  or  partially 
altered  to  hornblende  or  uralite. 

Microscopically  the  augite  gabbros  are  found  to  be  pre- 
dominantly hypautomorphic-granular  in  texture,  occasionally 
becoming  ophitic.  The  augite  and  plagioclase  may  be  fresh,  or 
partially  or  completely  altered;  and  the  alteration  of  these  minerals 
seems  to  have  proceeded  independently,  for  fresh  augite  may  be 
associated  with  altered  plagioclase,  and  vice  versa.  The  plagio- 
clase may  be  partially  altered  to  sericite,  or  flecked  with  sericite 
and  partially  replaced  by  quartz  or  epidote.  The  augite  may  be 
partially  or  completely  altered  to  compact  green  hornblende  or  to 
an  aggregate  of  uralite  fibers  or  of  uralite,  quartz,  and  chlorite. 
The  ilmenite  is  usually  altered  to  leucoxene  and  is  very  small  in 
amount.  Pyrite  is  rare  and  magnetite  relatively  abundant.  The 
peak  of  Holyrood  Butterpot  is  formed  of  an  elliptical  mass  of 
gabbro  about  1,200  feet  by  500  feet,  completely  surrounded  by 
granite.  It  is  peculiar  in  having  quartz  in  small  amount  filling  the 
interstices  between  the  feldspars  in  such  a  manner  as  to  indicate 
its  origin  as  an  original  constituent,  the  last  product  of  crystalliza- 
tion. Some  of  the  augites  are  twinned,  and  others  show  idio- 
morphic  basal  sections.  A  chemical  analysis  of  this  rock  is  given 
on  page  476,  No.  2. 


474  A.  F.  BUDDINGTON 

About  six  miles  south  of  Manuels,  lying  between  a  series  of  green 
slates  and  the  Holyrood  granite,  a  more  or  less  elliptical-shaped  mass 
of  gabbro  forms  a  conspicuous  ridge  in  the  topography.  This 
gabbro  has  a  tendency  toward  a  gneissic  structure  but  without  any 
particular  evidences  of  dynamic  metamorphism.  It  is  quite  inti- 
mately penetrated  by  ramifying  apophyses  of  granite  and  by  epidote 
veins,  which  are  especially  common  along  the  joint  planes.  In  thin 
section  the  rock  is  seen  to  be  hypautomorphic  granular  to  ophitic 
in  texture  and  to  consist  essentially  of  light-green  hornblende  and 
labradorite.  The  feldspars  are  extensively  altered  to  sericite,  and 
some  of  the  hornblende  to  intergrown  fibers  and  blades  of  epidote, 
zoisite,  and  quartz.  Many  of  the  hornblendes  are  twinned  parallel 
to  the  orthopinacoid,  and  by  an  occasional  resemblance  of  crystal 
form  give  indications  of  an  apparently  primary  origin.  Whether 
this  rock  is  the  result  of  recrystallization  during  the  intrusion  of  the 
granite  or  whether  it  is  primary  is  difficult  to  say.  A  chemical 
analysis  is  given  on  page  476,  No.  i.  In  this  connection  it  may  be 
well  to  note  that  where  the  road  crosses  Seal  Cove  Brook  there  is 
an  outcrop  of  hornblende  porphyrite  with  phenocrysts  of  hornblende 
up  to  10  mm.  in  length  and  plagioclases  averaging  2-3  mm.  in 
length.  In  thin  section  this  rock  is  found  to  consist  of  idiomorphic 
phenocrysts  of  labradorite  and  hornblende  in  a  groundmass  in  some 
places  consisting  of  a  microcrystalline,  elsewhere  of  an  almost 
crypto-crystalline,  aggregate  of  plagioclase  microlites,  quartz, 
and  an  altered  ferromagnesian  mineral  in  sparse  amount.  The 
plagioclases  show  a  zonary  banding. 

To  the  west  and  south  of  Woodfords  is  a  stock  of  granodiorite 
about  two  miles  long  and  one-half  mile  wide,  intrusive  into  the  beds 
of  the  Avondale  volcanic  series.  Dikes  from  this  mass  are  excep- 
tionally rare,  but  enough  evidence  was  found  to  prove  its  intrusive 
nature.  The  rock  is  light  colored  and  medium  grained,  consisting 
of  pink  orthoclase,  black  hornblende,  and  quartz.  The  latter  is 
abundant  in  small  grains  which  show  upon  a  fresh  surface  only  when 
closely  examined.  On  the  weathered  surface,  however,  they  stand 
out  in  relief  and  give  to  the  rock  the  appearance  of  a  typical  granite. 
With  the  microscope  the  rock  is  found  to  consist  of  andesine,  ortho- 
clase, augite,  and  quartz,  with  abundant  rods  and  grains  of  apatite. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  475 

The  colorless  augite  is  almost  completely  altered  to  pleochroic  green 
hornblende  and  chlorite.  A  chemical  analysis  of  this  rock  is  given 
on  page  476,  No.  3. 

Outcrops  of  a  quartz  syenite  are  found  along  the  shore  to  the 
north  of  Chapel  Cove.  This  rock  has  a  very  limited  distribution, 
occurring  in  fault  blocks  brought  into  their  present  position  by 
thrusting,  and  in  places  the  rock  is  much  crushed  by  the  stresses 
to  which  it  has  been  subjected.  In  the  hand  specimen  the  rock 
appears  to  be  a  white,  medium-grained  syenite,  consisting  of  an 
aggregate  of  feldspars  averaging  5  mm.  in  length.  In  thin  section 
the  rock  is  seen  to  consist  of  an  aggregate  of  plagioclase  feldspars, 
predominantly  albite  and  to  a  minor  extent  oligoclase,  with  a 
groundmass  of  quartz  and  orthoclase  in  micrographic  intergrowth 
filling  the  interstices.  The  rock  is  crushed  and  exhibits  cataclastic 
texture  in  a  high  degree.  A  chemical  analysis  of  this  rock  will  be 
found  on  page  476,  No.  4. 

The  backbone  of  the  St.  John's  Peninsula  is  mapped  by  Howley 
(1907)  as  Laurentian.  This  rock  in  its  northern  half  was  found  by 
the  writer  to  bear  intrusive  relations  to  the  Avondale  volcanics  and 
to  constitute  a  granite  batholith  five  to  six  miles  in  width  and  about 
forty  miles  in  length,  if  its  boundary  to  the  south  continues  to 
coincide  with  that  of  Howley's  Laurentian  area.  The  eastern 
boundary,  where  it  was  followed  by  the  writer  for  several  miles,  is 
delimited  by  a  fault  plane.  Along  the  west  side  the  beds  are  very 
much  disturbed  and  folded.  The  rock  is  a  pink,  medium-grained, 
equigranular,  biotite  granite,  consisting  essentially  of  quartz, 
orthoclase,  albite,  oligoclase,  and  chlorite,  the  latter  believed  to  be 
derived  from  biotite.  Fresh  flakes  of  original  biotite,  however,  are 
found  only  in  occasional  sections.  A  chemical  analysis  of  the  rock 
appears  on  page  476,  No.  5. 

One  of  the  most  striking  and  interesting  features  of  the  geology 
along  Smith  and  Random  sounds  at  the  head  of  Trinity  Bay  is  the 
way  in  which  the  early  green  slates  of  that  region  have  been  rent, 
riven,  and  intruded  by  a  great  series  of  approximately  parallel  dikes 
of  porphyrite  and  basalt.  At  .one  locality  there  were  counted  32 
dikes  in  a  distance  of  about  350  yards.  As  a  rule,  however,  the 
dikes  are  not  as  frequent  as  this ;  yet  they  are  never  absent  for  any 


476 


A.  F.  BUDDINGTON 


great  distance.  Their  general  strike  is  approximately  north-south. 
About  half  the  dikes  are  between  two  and  five  feet  in  width,  and 
the  rest  are  about  equally  divided  between  dikes  ten  to  fifteen  feet 
and  those  thirty  or  more  feet  in  width.  In  addition  to  the  dikes 
in  the  slate  series  several  dikes  and  sills  were  found  intruding  the 
Cambro-Ordovician  rocks,  and  dikes  in  the  Signal  Hill  and  Random 
formations  are  present  but  rare.  The  porphyrite  dikes  are  variable 
in  their  mineralogical  composition  and  comprise  hornblende  por- 
phyrites,  labradorite  porphyrites,  and  augite  porphyrites  or  basalts. 

TABLE  V 

CHEMICAL  ANALYSES  OF  INSTRUCTIVE  IGNEOUS  ROCKS  AROUND  CONCEPTION  BAY 


i 

2 

3 

4 

5 

SiO2 

4.8    =C4 

r  i    -IA 

irn    ig 

60    ^2 

71  82 

A12O3 

2O   62 

ox  -OH- 
l8   Q4 

18  21 

16  85 

16  07 

Fe2O3 

r    -2Q 

-2    20 

2    73 

Q7 

I    22 

FeO 

c    c-i 

6  4.0 

1    62 

i  6=: 

I    60 

MgO 

4   77 

A    cc 

2    c;i 

18 

4O 

CaO                           

8  16 

8  84 

4    23 

I    37 

i  66 

Na2O*  

3  •  14 

2  .  10 

3   84 

^    OQ 

3    27 

K2O  

i  .  23 

I  .OQ 

3   26 

•2   7? 

3   07 

H2O+  

1.85 

2.12 

1.85 

.89 

71 

H2O-  

•  *7 

.  II 

.  20 

•  CX 

•  J9 

TiO2  

.  20 

•  34 

Undet. 

.  21 

Undet. 

MnO  

•  19 

.29 

.16 

.09 

•  13 

Total 

00   77 

00    ^0 

00    70 

oo  66 

100  14 

1.  Hornblende  gabbro  from  about  6  miles  south  of  Manuels. 

2.  Quartz  bearing  gabbro  from  Holyrood  Butterpot. 

3.  Granodiorite  from  near  Woodfords. 

4.  Quartz  syenite  from  Chapel  Cove. 

5.  Biotite  granite  from  interior  of  St.  John's  Peninsula. 

The  former  are  found  in  the  pre-Cambrian  slates,  but  only  the  last 
named  in  the  Cambro-Ordovician  beds. 

In  the  region  about  Conception  Bay  the  granite  of  the  Holyrood 
batholith,  the  gabbro,  quartz  syenite,  and  dikes  of  rhyolite  porphyry 
and  diabase  are  all  overlain  'unconformably  by  Lower  Cambrian 
sediments.  Salic  dikes  were  not  found  intruding  beds  younger  than 
the  Conception  slate  series,  and  femic  dikes  are  far  less  frequent  in 
formations  above  this  series  than  in  those  below  it  and  constituting 
it.  Whether  this  is  due  to  the  different  character  of  the  formations, 
to  their  different  stratigraphic  position,  or  to  their  different  age, 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  477 

is  an  open  question.  What  little  evidence  there  is  seems  to  point 
toward  a  period  of  batholithic  and  dike  intrusion  at  a  time  succeed- 
ing the  period  of  deposition  of  the  Conception  series  and  preceding 
that  of  the  Signal  Hill  series.  No  dikes  whatever  were  found  intrud- 
ing the  Cambro-Ordovician  beds  in  the  region  of  Conception  Bay, 
but  in  the  vicinity  of  Trinity  Bay  infrequent  dikes  of  a  distinctive 
character  do  intrude  these  beds  and  undoubtedly  belong  to  a 
younger  period  of  intrusion,  possibly  that  of  the  Taconic  revolution, 
or  related  to  the  period  of  vulcanicity  represented  by  vast  flows 
of  lava  in  the  Notre  Dame  Bay  region  about  fifty  miles  to  the  north- 
east. This  period  of  intrusion  during  the  pre-Cambrian  corresponds 
to  a  similar  period  of  intrusion  of  granite  into  the  volcanic  series 
of  the  Blue  Ridge  of  Maryland  and  Virginia  described  by  £eith 
(1892),  or  the  Proterozoic  batholiths  of  the  Lake  Superior  region 
described  by  Allen  (1915,  p.  717)  which  he  suggests  are  post-Middle 
Huronian  or  pre-Upper  Huronian. 

Geographically,  chemically,  and  physically  the  volcanics, 
plutonics,  and  dikes  of  the  Conception  Bay  region  appear  to  be 
genetically  allied.  Thus  the  gabbros,  quartz-bearing  gabbro, 
hornblende  porphyrite  with  quartzose  groundmass,  granodiorite, 
quartz  syenite,  biotite  granite,  granophyre,  and  aplite  form  a  series 
of  rocks  with  an  ascending  silica  ratio,  belonging  to  the  same 
geographical  area  and  very  probably  to  the  same  period  of  intrusion. 
Again,  the  analyses  of  the  Holyrood  granite,  rhyolite  porphyry  near 
Holy  rood,  and  a  rhyolite  flow  from  the  Avondale  volcanics  near 
Manuels,  constituting  a  batholith,  a  volcanic  neck,  and  a  volcanic 
flow  respectively,  show  but  slight  variation  in  composition,  although 
the  texture  varies  widely.  The  chemical  differences  between  the 
granite  on  the  one  hand,  and  the  rhyolite  porphyry  and  rhyolite  on 
the  other,  are  the  usual  relative  increase  in  silica  and  loss  of  alumina, 
lime,  magnesia,  and  iron  in  the  volcanic  facies.  Again,  the  plu tonic 
gabbros,  a  volcanic  plug  of  plagioclase  basalt  near  Manuels,  and 
the  Blue  Hills  basalt  flows  may  be  cited  as  textural  facies  of  a  similar 
basic  magma.  The  repeated  recurrence  and  abundance  of  intru- 
sions of  magma  of  basaltic  composition  in  dikelike  form  throughout 
the  entire  peninsula,  in  contrast  to  the  restricted  local  character  of 
the  salic  intrusions  with  their  associated  infrequent  dikes,  rather 


478  A.  F.  BUDDINGTON 

impress  one  with  the  idea  that  a  basaltic  magma  was  the  one  from 
which  the  salic  differentiates  originated. 

• 

CONCLUSION 

The  points  brought  out  in  this  paper  which  it  is  desired  to 
emphasize  are  as  follows: 

1 .  The  confirmation  of  the  local  glaciation  of  the  Avalon  Penin- 
sula, of  the  control  of  faults  and  fractures  over  the  lineaments  of  the 
topography,  and  of  the  fiord  nature  of  the  coast. 

2.  The  description  and  confirmation  of  the  presence  of  a  thick 
series  of  volcanics  at  the  base  of  the  pre-Cambrian  section. 

3.  The  presentation  of  evidence  pointing  toward  the  origin  of 
the  members  of  the  later  pre-Cambrian  series,  as  follows : 

a)  The  Avondale  volcanics  as  subaerial  accumulations  of  vol- 
canic materials  derived  from  volcanoes  of  the  central  type. 

b)  The  Conception  slate  series  as  materials  derived  from  rocks 
resembling  the  Avondale  volcanics  swept  into  the  sea  in  a  com- 
paratively fresh,  unaltered  condition. 

c)  The  Momable  formation  as  well-decomposed  marine  sedi- 
ments with  traces  of  organic  life. 

d)  The  Signal  Hill  reddish-brown  sandstone  series  as  dominantly 
subaerial  fluviatile  deposits  in  a  subarid  climate,  derived  from  a 
re-working  of  volcanic  rocks  resembling  members  of  the  Avondale 
volcanics. 

4.  The  evidence  of  a  comagmatic  series  of  igneous  rocks  intruded 
probably  at  some  time  during  early  or  middle  Proterozoic  time. 

5.  The  entire  series  from  bottom  to  top  is  derived  directly  or 
indirectly  from  rocks  of  volcanic  origin. 

The  author  wishes  to  acknowledge  his  indebtedness  to  Professors 
van  Ingen  and  Smyth  for  their  cordial  assistance  and  advice 
rendered  to  him  throughout  the  course  of  the  work,  and  to  Mr.  B.  F. 
Howell  for  his  assistance  during  the  summer  of  1913. 


PRE-CAMBRIAN  ROCKS  OF  NEWFOUNDLAND  479 

BIBLIOGRAPHY 

Allen,  R.  C.     "Revision  of  the  Correlation  of  the  Huronian  Group  of  Michigan 

and  the  Lake  Superior  Region,"  Jour,  of  GeoL,  XXIII,  No.  8  (1915), 

pp.  705-24. 
Blackwelder,   Eliot.     "Summary  of   the  Orogenic  Epochs  in  the   Geologic 

History  of  North  America,"  ibid.,  XXII,  No.  7  (1914),  pp.  633-54. 
Buddington,  A.   F.     "  Pyrophyllitization,   Pinitization,   and  Silicification  of 

Rocks  around  Conception  Bay,  Newfoundland,"  ibid.,  XXIV   (1916), 

130-52. 
Daly,  R.  A.     "  Geology  of  the  Northeast  Coast  of  Labrador, "  Harv.  Coll.  Mus. 

Comp.  Zool.  Bull.,  XXXVIII  (1902),  205-70. 
Howley,  J.  P.     Geological  Map  of  Newfoundland,  1907. 
Jukes,  J.  B.     General  Report  of  the  Geological  Survey  of  Newfoundland  during 

the  Years  1839  and  184.0.     London:  John  Murray. 
Keith,  Arthur.     "Geologic  Structure  of  the  Blue  Ridge  in  Maryland  and 

Virginia,"  Am.  GeoL,  X  (1892),  362-68. 
Malcom,  Wyatt.    Gold  Fields  of  Nova  Scotia.     Canada  Geol.  Surv.,  Mem. 

No.  20,  1912. 
Murray,  A.  and  Howley,  J.  P.    Geological  Survey  of  Newfoundland.    London: 

Edward  Stanford. 
Walcott,  C.  D.     "  Pre-Cambrian  Fossiliferous  Formations,"  GeoL  Soc.  Am. 

Bull.,  X  (1899). 
.     "Random,  a  pre-Cambrian  Upper  Algonkian  Terrane,"  ibid.,  XI 

(1900),  3-5. 


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